Everything I do leads me in a circle, of either the x's cancelling, or me getting no where. Can anyone direct me the right way, how should I set up the problem? Thanks.

Here's the question, I need help on Q2)a)i):

When the depth of water is metres, suppose that the volume of water is . Then if the time is measured in minutes, the rate of increase of with respect to is . This is the rate at which water is filling the tank.